Re: Wrong tree
"The telcos need to enforce caller ID and anonymous call blocking properly"
A good analogy for this is to think of it in terms of letter delivery.
It's as if we asked letter senders to write their address on the back of an envelope and then demanded that the postal service who actually put it through the delivery letterbox only do so if they've validated that the sender's address on the back is correct. How would they know? It's the same problem. If one organisation handled the whole thing end-to-end it's possible, but globally? That's a tough call.